It is proposed to study the structure, conformation, and modes of interaction of several members of a number of biologically-important molecules. The principal technique used will be X-ray structure analysis on a series of crystalline derivatives of the compounds in question. Comparisons will be made between different members of a series with a view to determining the most important requirements for biological functions. Three-dimensional molecular graphics will be used for these comparisons. Where appropriate high resolution nuclear magnetic resonance will be used to establish whether the conformation found in the crystal persists in solution. The classes of molecules being studied include the ionophore, X537A (lasalocid), the peptide antibiotic vernamycin, the ansamycin antibiotic streptovaricin, and two macrocyclic antibiotics, about which relatively little is known, hedamycin and berninamycin. Some studies are also proposed among nucleoside and dinucleotide analogs. Some proposals are also made for some solid state chemistry in biological systems. BIBLIOGRAPHIC REFERENCES: "Synthesis and Structural Determination of Dehydrocyclobutatusin, A Diterpenoid with a Four-Membered Ring," by R. Zelnik, J. A. McMillan, I. C. Paul, D. Lavie, V. G. Toscano, and R. R. DaSilva, J. Org. Chem., 42, 923 (1977). "Molecular Structure of Kodo-Cytochalasin-l" by J. A. McMillan, C. C. Chiang, M. K. Greensley, I. C. Paul, S. A. Patwardhan, S. Dev, M. A. Beno, and G. G. Christoph, J.C.S. Chem. Commun., 105 (1977).